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Short-term toxicity to fish

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Reference
Endpoint:
short-term toxicity to fish
Type of information:
experimental study
Adequacy of study:
key study
Study period:
no data
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH
1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The reaction mass of sulphuric acid, hydrogen peroxide and peroxomonosulphuric acid is predominantly sulphuric acid (>80%). Although all constituents of the reaction mass contribute towards and are essential for the desired technical effects of the range, it is considered acceptable to read-across to data on sulphuric acid. This because significant toxicological effects are likely to be masked in the multi-constituent substance by its corrosive nature and so it considered appropriate to read across to the mean constituent, sulphuric acid, when considering aquatic toxicity.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
See read-across data matrix under 'Attached background material' below.

3. ANALOGUE APPROACH JUSTIFICATION
See read-across data matrix under 'Attached background material' below.

4. DATA MATRIX
See read-across data matrix under 'Attached background material' below.
Qualifier:
no guideline followed
Principles of method if other than guideline:
The effect of hydrogen ion concentration on the mortality of the bluegill sunfish was quantified.
GLP compliance:
no
Remarks:
study pre-dates GLP
Analytical monitoring:
yes
Details on sampling:
Not reported
Vehicle:
no
Details on test solutions:
- Lethal concentrations for four acids (H2SO4, HNO3, HCl and H3PO4) were determined on groups of eight fish transferred into each of five aquaria, initially maintained at pH 7.5.
- After a stabilisation period of one week, the fish in four of the aqauria were subjected to increasing concentrations of each acid so that the pH was decreased.
- During the 96 h interval at each pH, acid was added as needed to maintain constant pH and fish mortality was monitored at 24, 48 and 96 h.
- Fish mortality was also monitored at the same times in the remaining aquarium in which the fish were not subjected to acid and remained at pH 7.5.
- To eliminate the possibility that an infectious agent may have been the cause of death in acid treated aquaria, some acid treated aquaria which had 100 % mortality were neutralised with sodium hydroxide to return the water to pH 7.5. Eight fish were then added to each neutralised aquarium and mortality was determined.
Test organisms (species):
Lepomis macrochirus
Details on test organisms:
- Bluegill of approximately 4 cm were obtained from a state fish hatchery (Louisiana, USA).
- Fish were separated into groups of 30 in the laboratory and maintained in 38 L aquaria (51 x 32 x 27 cm) containing dechlorinated tap water.
- Fish were subjected to continuous light and were fed tropical fish food or brine shrimp each evening.
- External air filters containing glass wool and activated charcoal were used on all aquaria.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
96 h
Post exposure observation period:
Not applicable
Hardness:
Not reported
Test temperature:
23 ± 2 °C
pH:
Fish were initially maintained at pH 6.5
Dissolved oxygen:
Not reported
Salinity:
Not applicable
Nominal and measured concentrations:
Decreasing pH series of 7.5, 5.0, 4.5, 4.0, 3.5, 3.25 and 3.0
Details on test conditions:
- Locomotor activity experiments were conducted in the 38 L aquarium with 30 fish.
- During the experiment, each aquarium was divided into two identical compartments (A and B) by inserting a clear Plexiglas partition containing one diamond-shaped opening (70 cm2 in area) in the centre of the partition.
- Prior to the experimental run, all aeration and filtration devices were removed.
- The 30 bluegill were pushed to one half of the aquarium (compartment A) by means of a porous screen.
- After the fish voluntarily distributed themselves in a random fashion in compartment A, usually within 5 minutes, the porous screen was removed leaving only the Plexiglas partition.
- The fish were then allowed to disperse throughout the aquarium.
- The number of fish found in compartment B was determined every 15 s for 9 min after removal of the porous screen.
- To determine the effects of sulphuric acid on mortality, a rate constant was first established on fish prior to the time of acid introduction.
- The pre-treatment period lasted for 10 days.
- After the pre-treatment period, the aquarium was adjusted to pH 4.0, and a rate constant determined over a period of 10 days acid exposure.
- In this way the locomotor activity of each group after exposure to acid was compared to activity of the same group prior to exposure.
- Kinetic experiments were conducted twice a day.
- All data were pooled to derive a single overall rate constant for both the 10 d pre-treatment and 10 d treatment periods.
Reference substance (positive control):
no
Duration:
96 h
Dose descriptor:
LC50
Effect conc.:
> 16 - < 28 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality (fish)
Details on results:
- No acute mortality was observed in any acid until the pH reach 3.25.
- Mortality was 100 % for all acids when pH reached 3.0.
- No mortality was observed among fish introduced into aquaria (previously found to be toxic at pH 3.0) after the hydrogen ion concentration was returned to pH 7.5 by addition of sodium hydroxide.
- Rate constant for bluegill locomotor activity before exposure to sulphuric acid (pH 7.5) was 0.118.
- Rate constant for bluegill locomotor activity after exposure to sulphuric acid (pH 4.0) was 0.026.
- The rate constants demonstrate that fish were one quarter as active after exposure to sulphuric acid.
Results with reference substance (positive control):
Not applicable
Reported statistics and error estimates:
Not applicable
Sublethal observations / clinical signs:

JUSTIFICATION FOR USE OF READ-ACROSS DATA

See comparison of overall physico-chemical and toxicity profiles for target and source chemicals in the data matrix (attached).

MORTALITY OF FISH EXPOSED TO ACIDS

Acid

Exposure (h)

Percentage mortality *

pH 5.0

pH 4.5

pH 4.0

pH 3.5

pH 3.25

pH 3.0

H2SO4

24

0

0

0

0

100

100

48

0

0

0

0

100

100

96

0

0

0

50

100

100

HNO3

24

0

0

0

0

63

100

48

0

0

0

0

63

100

96

0

0

0

0

100

100

HCl

24

0

0

0

0

75

100

48

0

0

0

0

75

100

96

0

0

0

0

88

100

H3PO4

24

0

0

0

0

13

100

48

0

0

0

0

13

100

96

0

0

0

0

13

100

*

No fish died in control aquaria maintained at pH 7.5

Validity criteria fulfilled:
not applicable
Conclusions:
The LC50 was found to lie between pH 3.5 and pH 3.0 (equivalent to 16 to 28 mg/L) for sulphuric acid and three other acids. The authors conclude that any contribution by the anions of the acids is similar and that the quantity rather than the quality of acids is the primary factor.

Description of key information

LC50 16 to 28 mg/L (pre-GLP assessment of bluegill sunfish exposed to acids)

Key value for chemical safety assessment

Fresh water fish

Fresh water fish
Effect concentration:
16 mg/L

Additional information

Sulphuric acid, peroxomonosulphuric acid and hydrogen peroxide are each expected to contribute to the physico-chemical properties of the multi-constituent substance. However, significant toxicological effects are likely to be masked in the multi-constituent substance by its corrosive nature. It is therefore considered appropriate to read-across to the main constituent, sulphuric acid, when considering aquatic toxicity (LC50 equates to pH 3.0 to pH 3.5).

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